The present invention relates to a device for making a fluid having electrical conductivity flow.
A prior art electromagnetic flow coupler has been proposed which includes rectangular duct 41 with a partitioning plate 42 so that two separate fluids having electrical conductivity may flow therethrough, i.e., so as to form two ducts one of which is a primary duct 43 and the other of which is a secondary duct 44. A driving fluid 45 and a driven fluid 46 are caused to respectively flow through the primary duct 43 and the secondary duct 44. The outer surface of the rectangular duct 41 is enclosed by an electrode 47 formed of good electrical conductor, whereby both ducts 43, 44 are constructed into a current circuit. At both sides of the rectangular duct 41, there are provided a pair of magnets 49 so that a common magnetic field 48 is imparted to both the driving fluid 45 and the driven fluid 46.
When the driving fluid 45 flows through the primary duct 43 by an external force, a current 50 is induced in the driving fluid 45 in accordance with the Fleming's right-hand rule in a direction perpendicular to the direction of the magnetic field 48 and the flowing direction of the driving fluid, respectively. The electric current 50 thus induced is supplied to the driven fluid 46 existing in the secondary duct 44 by passing through the electrode 47 provided on the outer peripheral surface of the rectangular duct 41. In the driven fluid 46 thus supplied with the current, a pumping force is produced in accordance with the Fleming's left-hand rule in a direction perpendicular to the directions of the magnetic field 48 and the supplied current, respectively. When the common magnetic field 48 and the current 50 are respectively oriented in the above-mentioned directions, the driving fluid 45 and the driven fluid 46 flow in mutually opposite directions as shown in FIG. 1 by enlarged white arrows.
An electromagnetic flow coupler disclosed in a Japanese Patent Unexamined Publication No. 10163/1984, shown in FIG. 2, is known as an example of the electromagnetic flow coupler having a structure based on the above-mentioned principle.
The conventional electromagnetic flow coupler of FIG. 2 has an outer duct 51 made of stainless steel such as SUS 316 in order to obtain a mechanical strength of the duct 51 and, at the same time, prevent the leakage of liquid metal. A duct 52 made of material having electrical conductivity such as copper is provided, as an electrode, inside the outer duct 51. Further, an insulating member 53 including alumina plate is provided at each side of electrode in order to prevent electricity from leaking from a portion thereof. At a substantially central portion of the inside duct 52, an electrically conductive isolation plate 54 is disposed vertically with respect to the insulating member 53 on each side of the inside duct 52 so as to form two adjacent separate fluid passages, i.e., first fluid passage 55 and a second fluid passage 56.
The surfaces of the first and second fluid passages 55, 56 which contact with the fluid are applied with inner linings 57 include thin stainless steel plates in order to prevent the corrosion of the insulating members 53 and relevant portions of the inside duct 52. The inside duct 52, insulating members 53 and inner linings 57 are fixed by bolts, nuts, ribs, etc.
When magnetic fields are formed in the direction indicated by arrows 59, the liquid metal, for example, sodium, which flows through the first fluid passage 55 by the action of, for example, an external pump (not shown), has a current induced therein in a direction perpendicular to the flowing direction of the sodium as well as to the direction of the magnetic field. Accordingly, the first fluid passage 55 causes a D.C. power generating function, and the resultant induced current flows out from a top thereof, flowing back into a bottom of the second fluid passage 56, as indicated by arrows 60. Since the side walls of the fluid passages 55, 56 are electrically insulated almost as a whole by the insulating members 53, the induced current flows through the second fluid passage 56. In the fluid inside the second fluid passage 56, a force is produced in a direction perpendicular to the flowing direction of the induced current and the acting direction of the magnetic field, with the force serving as a pumping force for causing a flowing of the liquid sodium in the second passage 56.
As shown in FIG. 2, it is necessary to provide a bus bar electrode to enclose the duct in order to supply a low-voltage/large-current induced in the first passage 56, 55 to the second passage for using it in the form of a driving current which permits the second passage 56 to act as a pumping section. Besides, the insulating member is required to be provided on both sides of the duct in order to obtain a larger amount of orthogonal component current effective to produce the pumping force and to prevent the leakage of electricity from the electrode portion through the duct wall. With the above-mentioned construction, the arrangement functions as an electromagnetic flow coupler, in principle. However, where the fluid is, for example, sodium, corrosion prevention measures should be taken with respect to the insulating members or bus bar portions. In this view, in the conventional arrangement shown in FIG. 2, the inner linings consisting of stainless steel plate (SUS plate) are applied onto the inner surface of the duct.
As stated above, the prior art electromagnetic flow coupler has a complicated structure including the means of attaching the respective constituent elements. Further, when viewed from the aspect of performance, the low-voltage/large-current flow path has a structure wherein the joining portion between the inner linings and bus bar has an increased electrical contact resistance. Furthermore, in the prior art, no consideration is given to the power dissipation due to the short-circuit current at the electrode portions which does not serve as a pumping power.
It has been determined that such electromagnetic flow coupler can be utilized as a flowing means used when the fluids in the passages of a two-flow system simultaneously flow in opposite directions as in case of a liquid sodium heat exchanger arranged to transfer heat from the passage of one flow to the passage of the other flow.
A conventional liquid sodium heat exchanger as shown in FIG. 3, is a shell-and-tube type heat exchanger, which is among the heat exchangers disclosed in "Liquid Metal Handbook (Sodium and Nak Supplement)" 1967-6 published by a United States LMEC.
The illustrated type of heat exchanger is used for transferring heat from a primary cooling section to a secondary cooling section incorporated in a fast breeder reactor (hereinafter, referred to simply as "fast breeder") constituting a nuclear reactor. As shown in FIG. 4, the cooling system of the fast breeder includes a primary cooling section, secondary cooling section and steam generating section. Within a reactor vessel 101, a reactor core 102 is disposed and a primary coolant 103 such as liquid sodium, an electrically conductive fluid, is filled. The reactor vessel 101 is provided at its bottom with an inlet nozzle and at its top with an outlet nozzle. The inlet nozzle portion is connected with a pump for the primary cooling section while the outlet nozzle portion is connected with an intermediate heat exchanger 105 through a pipe 106, to form the primary cooling section 107. On the secondary side of the intermediate heat exchanger 105, a pump 108 for the secondary cooling section is connected thereto and a steam generator 109 is also connected through a pipe 110, to form the secondary cooling section 111. On the secondary side of the steam generator 109, there is connected a water feeding pump 112 as well as a steam turbine 114 directly connected with a power generator 113 through a pipe line 115, to form the steam generating section 116. The heat generated from the reactor core 102 is transferred by the coolant 103 flowed by operation of the pump 104, toward the intermediate heat exchanger 105. In the secondary cooling section 111, the heat of the intermediate heat exchanger 105 is transferred toward the steam generator 109 by operation of the pump 108. The steam generator 109 heats the water from the water feeding pump 112 by the heat thus transferred, into a superheated steam which is then fed to the steam turbine 114 to drive the same, to thereby rotate the power generator 113 so as to abtain electricity from the generator 113.
In the above-mentioned cooling system, since the primary cooling section circulates the radioactive coolant, the heat from the reactor core 102 is once transferred, for ensuring safety, to the non-radioactive coolant in the intermediate heat exchager 105 of the secondary cooling section 111 and thereafter a superheated steam is obtained as mentioned above.
As shown in FIG. 3, a shell-and-tube type heat exchanger includes a plurality of heat transfer tube 122 disposed within the cylindrical shell 121 and supported between an upper tube sheet 123 and a lower tube sheet 124 to form a bundle of tubes 125. This bundle of tubes 125 is supported by a support means 126 provided inside the shell 121. An upper plenum 127 and a lower plenum 128 are thus provided on the upper tube sheet 123 and under the lower tube sheet 124, respectively.
At the upper portion of the shell 121 falling within a zone where the bundle of tubes 125 is provided, a primary inlet nozzle 129 is provided, and, at the lower portion thereof, a primary outlet nozzle 130 is provided. A secondary inlet nozzle 131 is provided at the lower plenum 128 while a secondary outlet nozzle 132 is provided at the upper plenum 127. In the intermediate heat exchanger 105 having the above-mentioned construction, a heating fluid 133 is introduced from the primary inlet nozzle 129 by an external pump and passes over the outer peripheries of the heat transfer tubes 122 and then flows out from the primary outlet nozzle 130. On the other hand, the fluid 134 to be heated is introduced from the secondary inlet nozzle 131 by pump and is allowed to flow into the heat transfer tubes 122 from the lower plenum 128, flowing through the interiors of the heat transfer tubes 122 to join together into the upper plenum 127. Thus, the fluid flows out from the secondary outlet nozzle 132. Accordingly, in the area of the bundle of heat transfer tubes 125, the flow of heating fluid 133 and the flow of fluid 134 to be heated are opposite in direction to each other with the heat transfer walls intervening in between, whereby heat exchange is effected between both fluids 133 and 134.
As stated above, in order to operate the prior art intermediate heat exchanger, it is necessary to provide the primary and secondary pumps (104, 108) as supplementary instruments. Since the radioactive fluid flows in the primary cooling section, the machinery used therein is very difficult to maintain. High reliability, therefore, is demanded of the machinery in this regard. The pumps 104, 108 of mechanical system in particular contain rotary parts, for which reason they are most likely to cause an accident. A simple arrangement which eliminates the necessity of having such machinery is desirable. In the prior art, however, the use of both pumps 104 and 108 is inevitable.
It has been found that where a primary coolant is made to flow through one duct of electromagnetic flow coupler with a secondary coolant being made to flow through the other duct thereof, when only one of the two coolants is made to flow by a pump, the other coolant is caused to flow without using a separate pump to enable a heat exchange between both coolants. In this case, however, it is necessary to efficiently utilize the current induced in the power generating section of the electromagnetic flow coupler, as the pumping power therefor.